Table 1. Comparison of magnitude of changes (effect size) in the basic reproductive number in relevant observational or predictive studies.
| effect size (relative change in R0) |
Study | |
|---|---|---|
| Estimated changes c.1900 - 2007 | ||
| Proportion of 1900 endemic world by areaa | Current study | |
| 13% | ÷ ≤1b | |
| 12% | ÷ 1 - 10 | |
| 18% | ÷ 10 - 100 | |
| 57% | ÷ >100 | |
| Changes predicted under climate change | ||
| Spatially aggregated mean change by ~2050c,d | 14 | |
| P. falciparum | × 1.27 (1.16 - 1.74) | |
| P. vivax | × 1.23 (1.15 - 1.39) | |
| Range of local changes by ~2050d,e,f | × 0 - 2 | 14 |
| Range of local changes by ~2080d,f | × 0 - 2g | 13 |
| Range of local changes by ~2050d,e,f | × 0 - 3 | 12 |
|
Example effect sizes for interventions predicted via biological modelling |
||
| ACTs (compared to failing pre-ACT treatment) | ÷ 1.1 - 1.8h | 21 |
| ITNs (at 40-60% effective coverage) | ÷ 5 - 15i | 22 |
| ITNs + LCI (both at “moderate” coverage levels) | ÷ 15 - 25j | 23 |
|
Example effect sizes observed concurrently with increased intervention coverage (primary interventions in use) |
||
| Western Kenyak (ITNs, ITNs + LCI) | ÷ 7.2j, ÷ 26.4j | 25 |
| São Tomé and Principel (IRS + ITNs + ACT + IPTp) | ÷ 5.1m | 26 |
| Bioko Islandn (IRS + ACT) | ÷ 2.9o | 27 |
| Southern Mozambiquep (IRS + ACT) | ÷ 78.8q | 28 |
| Zanzibarr (ITNs + ACT); 0-5yrs, 6-14yrs | ÷ 1.6s, ÷ 1.8s | 29 |
ACT = Artemisinin-based Combination Therapy; EIR = Entomological Inoculation Rate; IPTp =Iintermittent Preventive Treatment in Pregnancy; ITN = Insecticide Treated Bednet; LCI = Larval Control Intervention
Percentages do not sum to 100 due to rounding.
Consists of 11% of land area with no evidence of change, and 2% with evidence of increased transmission.
The available results relate to the combined Africa, South-East Asia, Central and South America regions. Given are central modelled values and uncertainty intervals associated with plausible ranges of input biological parameters.
Results obtained using the MIASMA linked climate-biological model, under three future climate scenarios, and only the largest predicted changes are shown here.
In the original study, results were not presented for areas with very low baseline potential to avoid using infinitesimal values as denominators in the comparison.
Results apply to both P. falciparum and P. vivax.
Range of predicted changes included a ‘ >2 ’ category but no further details provided.
Study reported predicted changes in parasite rate from five real-world baseline endemicity settings under failing treatment regimes based on pre-ACT monotherapies (Table 4 in reference). We converted transitions in parasite rate into transitions in R0 to estimate effect size.
Study modelled effect size as a continuous function of ITN effective coverage. Values presented based on Figure 1 in reference.
Study reported effect sizes in terms of EIR, which were interpreted directly as R0 effect sizes.
Results from a control trial.
Integrated malaria control effort involving mass intervention coverage complemented with health system strengthening. Reported decline relates to period 2005-2007.
Study reported reduction in community parasite rate from 30.5% to 2.1% following expanded control efforts. We converted this into transitions in R0 to estimate effect size.
Integrated malaria control effort involving mass IRS administration, improved case management with ACT and strengthened health system surveillance and diagnostics. Reported decline relates to period 2004-2005.
Study reported reduction in community parasite rate from 46% to 31% following expanded control efforts. We converted this into transitions in R0 to estimate effect size.
Integrated malaria control effort involving IRS administration, improved case management with ACT and strengthened health systems. Reported decline relates to period 1999-2005.
Study reported reduction in community parasite rate from 65% to 4% in study zone with longest running intervention coverage (Zone 1, values taken from Table 1 of reference). We converted this into transitions in R0 to estimate effect size.
Integrated malaria control effort involving scale up of long-lasting ITNs from 10% to 90% coverage of children, switch from chloroquine to ACT as first and second line therapeutic and strengthened surveillance and health systems. Reported decline relates to period 2003-2005.
Study reported reduction in parasite rate in children 0-5yrs from 9% to 0.3% and in children 6-14yrs from 12.9% to 1.7% following expanded control efforts. We converted this into transitions in R0 to estimate effect size.